9-bit serial communication Linux how to receive data

别叫你哥许鲜森

9-bit serial communication Linux how to receive data [Copy link]

Crotex A8 kernel linux4.1.18

Using RS232 serial communication, the microcontroller sends 9 data bits, the highest bit 1 represents the address, and the highest bit 0 represents the data

The A8 core board receives data. Currently, it can only correctly receive bytes with the highest bit of 0 representing data and the highest bit of 1 representing the address. The result of receiving bytes is 00

Q: How can I correctly receive the data sent by the microcontroller?

angel_CN

It is recommended to read the datasheet, understand the RS232 protocol first, and then design the required timing according to the protocol.

Verifone

This is a standard duplex communication protocol, just write the program according to the protocol.

别叫你哥许鲜森

angel_CN posted on 2022-3-28 22:34 It is recommended to read the Datasheet, understand the RS232 protocol first, and then design the required timing according to the protocol

Hello, I have read the Datasheet document, but did not find the corresponding solution

别叫你哥许鲜森

Verifone posted on 2022-3-29 10:57 This is a standard duplex communication protocol. Just write the program according to the protocol.

Hello, our A8 core board needs to judge the highest bit (i.e. check bit) when receiving data. When the highest bit D8 is 1, D0-D7 represents the address; when the highest bit D8=0, D0-D7 represents the data; when I am receiving data sent by the microcontroller, the byte with D8=1 will report a check error

chunyang

What the OP has mentioned is already in the scope of the protocol, which requires software judgment. 232 itself does not care what the high bits are, whatever comes is connected, and how to parse it is another matter. The problem encountered by the OP is obviously caused by a problem in the software parsing programming.

别叫你哥许鲜森

chunyang posted on 2022-3-30 15:55 What the OP has mentioned is already in the scope of the protocol, which requires software judgment. 232 itself does not care what the high bit is, whatever comes is connected, how to parse it is another matter. ...

Thank you for your reply. Now it is a software problem. The hardware is OK.

Now I set the parity check of the serial port parameter c_cflag to 0, and then I want to ignore the check error PE when receiving the byte with the highest bit as 1, and read the contents of the RHR register.

chunyang

Don't call you brother Xu Xiansen posted on 2022-4-1 15:44 Thank you for your reply. Now it is a software problem. The hardware is connected. Now I set the serial port parameter c_cflag parity check to the highest bit as 0...

Then you can only use software to implement a virtual serial port. Hardware serial ports have different modes, and the 9-bit parity check mode cannot ignore the check error. And your protocol compilation is also very non-standard. You should use the command byte parsing function and express it in bits, which seriously lacks communication reliability.